1. Technical Field
The present disclosure relates to a monitoring camera which detects an object such as another vehicle or an obstacle in the vicinity of a vehicle, and a vehicle monitoring camera system which is capable of controlling a light distribution of a lamp or a vehicle traveling safety assistant based on the detected object.
2. Related Art
Recently, a technology has been proposed that obtains an image of a peripheral area of a subject vehicle using a monitoring camera, detects an object such as another vehicle or an obstacle in the vicinity of the subject vehicle, and displays the object on a monitoring device or controls a light intensity or a light distribution of a vehicle lamp such as a head lamp or a rear lamp in accordance with the detected objects. In this kind of monitoring camera, it is desirable to monitor a wide range in the vicinity of the vehicle, but it is necessary to mount multiple monitoring cameras each of which obtains images of different respective areas about the vehicle. One problem is that the manufacturing cost of such a monitoring camera is relatively high. For this reason, there has been proposed a monitoring camera capable of monitoring multiple areas using one monitoring camera. For example, JP-A-2007-13549 proposes a monitoring camera that simultaneously obtains images of three areas (i.e., a left area, a right area, and a down area) in the vicinity of the vehicle by using one imaging element. The monitoring camera is located in a rear portion of the vehicle, and an imaging lens and an imaging element are provided in the monitoring camera so as to obtain images of objects. Also, a mirror is provided in the monitoring camera so as to divide an imaging area by three reflection surfaces of the mirror. The three reflection surfaces of the mirror have reflection optical axes respectively facing a left direction, a right direction, and a downward direction.
In the monitoring camera described in JP-A-2007-13549, it is possible to obtain images of three areas using one imaging element. However, since an image of each area is formed on the imaging element using one imaging lens, the imaging magnification of each area is the same (i.e., the close object appears large, and the distant object appears small). Thus, when the images of the objects are displayed on the monitoring device, it is difficult to recognize the distant object (which appears too small). In addition, when the object is image-recognized based on an imaging signal of the object, since the distant object appears small, the resolution of the imaging element is low. Hence, in some cases, the distant object may not be detected through the image recognition. As a result, it often is not possible to monitor the distant area sufficiently, and thus it is not possible to exhibit a function of the monitoring camera sufficiently.
On the other hand, when an imaging lens having a long focal length is used, it is possible to obtain an image of the distant object so that it appears large, and also to increase the resolution of the imaging element. Accordingly, it is possible to recognize or detect the distant object. However, in this case, since the imaging viewing angle is narrow, an object at the side of the monitoring camera and particularly an object close to the monitoring camera are not included in the image viewing angle. Accordingly, it is hard to detect the objects through an imaging operation. For this reason, in the system in which the lighting operation of the vehicle is controlled by detecting the objects, illumination light emitted from the vehicle may result in glare to the adjacent vehicle, and hence the possibility of causing a critical accident may increase.